Car crashes are the leading cause of death for American children (according to a 2016 study). Cars are multi-ton machines capable of driving at high speeds that can only be stopped with effective brakes and fast reflexes by their drivers. Even a driver with fast reflexes is subject to human limitations. These limitations can be ameliorated by technology, such as brake lights on a car in front of the driver indicating that that car is in the process of braking, and therefore the driver should himself prepare to brake. But brake lights are binary and therefore serve as poor indicators of how quickly braking is necessary.
Brake lights, like many vehicle safety issues, are governed by strict regulations in many countries. For example, in the United States, commercial vehicle safety is regulated by 49 C.F.R. Chapter III, Subchapter B, and in particular Part 393, which regulates “Parts and Accessories Necessary for Safe Operation”. Passenger vehicle safety is regulated by 49 C.F.R. Chapter V, and in particular Part 571, which regulates “Federal Motor Vehicle Safety Standards”. For example, 49 C.F.R. § 571.108 specifies manufacturer-installed lamps, reflective devices, and associated equipment, including brake lights.
U.S. federal regulations specify macroscopic features of brake lights (e.g., color, minimum number of lights and their placement), but do not specify specific features such as shape of indicators or visible operation much beyond a simple on/off when brakes are applied. However, the effect of braking is more complex than can be described by a simple on/off indicator. For example, braking may be applied with a range of force, from a light tap that barely slows a vehicle, to a very hard press in a panic stop that may cause a skid even on dry pavement or activate an anti-lock brake system if installed. Different forces within this range have dramatically different effects upon vehicle deceleration, and consequently upon reactions that a driver in a vehicle behind the braking vehicle must make to try to avoid a collision.
However, a simple on/off indicator as in the known art provides no indication of a rate of deceleration to a following driver in a vehicle behind the braking vehicle. This may tend to cause dangerous situations. For example, a driver of the following vehicle may react too late to take evasive maneuvers, or may not brake soon enough or hard enough to avoid a collision. Conversely, a driver of the following vehicle may overreact by slowing too much or by taking unnecessary evasive maneuvers, thereby causing a collision with a third vehicle. Therefore, what is needed is one or more auxiliary lights that provides an indication of a rate of acceleration or of deceleration from braking, which lights are compatible with applicable safety regulations.